JP2008121668A - Power plant that utilizes gas turbine for power generation and process for lowering co2 emission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power plant and a process for lowering CO<SB>2</SB>emission. <P>SOLUTION: The power plant and the process generally include extracting a portion of a recirculated CO<SB>2</SB>-rich flue gas mid-way through a compression pathway of a gas turbine and removing the CO<SB>2</SB>in a separation unit. The remaining portion of the CO<SB>2</SB>-rich flue gas (i.e., the portion of the recirculated flue gas that was not fed to the separation unit) is mixed with fresh air coming from an additional compressor-expander and then fed back to the compression pathway. As a result, flue gas recirculation increases the CO<SB>2</SB>concentration within the working fluid, leading to an additional increase in CO<SB>2</SB>partial pressure. As the concentration and partial pressure of CO<SB>2</SB>is increased, a lower energy penalty is observed to remove the CO<SB>2</SB>. Moreover, a reduced volume is fed to the CO<SB>2</SB>separation unit during operation. Consequently, the size of the separation equipment can be reduced as well as the energy required for the separation process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates generally to a method for reducing CO ₂ emissions at a power plant that uses fossil fuels for power generation.

Carbon dioxide (CO ₂ ) emissions from power plants using fossil fuels are becoming more severely restricted by national and international regulations such as the Kyoto Protocol and EU Emission Trading Scheme. Yes. With increasing CO ₂ emission costs, reducing CO ₂ emissions is important for economic power generation. Today's CO ₂ removal technology is focused on reducing CO ₂ removal from the power plant's atmospheric flue gas stream, and the power plant contains very large and expensive energy-intensive CO _2. A removal unit is provided.

  Gas turbine plants operate in the Brayton cycle and typically compress the incoming air upstream of the combustion chamber using a compressor. The fuel is then introduced and ignited to generate a hot, high pressure gas that enters the turbine section and expands. The turbine section powers both the generator and the compressor. Combustion turbines can also burn a wide range of liquid and gaseous fuels ranging from crude oil to natural gas.

There are generally three methods currently employed to reduce CO ₂ emissions from such power plants. The first method is to recover the CO ₂ after combustion with air from the exhaust gas, absorption method and the resulting CO ₂ during combustion, adsorption, membrane separation, membrane, from the exhaust gas by cryogenic methods or a combination thereof Remove. This method, commonly referred to as post-combustion recovery, is typically focused on reducing CO ₂ emissions from the power plant atmospheric exhaust. The second method includes reducing the carbon content of the fuel. In this method, the fuel is first converted to H ₂ and CO ₂ before burning. Thus, the carbon content of the fuel can be recovered before being introduced into the gas turbine, and the production of CO ₂ is avoided. As a third method, there is an oxy fuel method (also referred to as an oxygen fuel method). In this method, pure oxygen rather than air is used as an oxidant to obtain flue gas consisting of carbon dioxide and water.

The main disadvantage of the post-combustion CO ₂ recovery method is that the CO ₂ concentration in the flue gas is low (usually 3 to 4% by volume in natural gas fuel power plants), so the CO ₂ partial pressure is low and expensive to remove CO ₂ Large-scale equipment is required. The CO ₂ concentration in the chimney, and thus the partial pressure, can be increased by partially recirculating the flue gas to the compressor of the gas turbine (see for example US Pat. No. 5,832,712), but still Quite low (about 6-10% by volume). The low CO ₂ partial pressure and large gas volume associated with post-combustion capture forms results in very high energy costs in addition to the very large and expensive equipment associated with CO ₂ removal.
US Pat. No. 5,832,712

Thus, there is a need for improved methods for efficiently removing CO ₂ from power plants.

Disclosed herein is a method for reducing CO ₂ emissions at power plants that use gas turbines and power plants that use fossil fuels for power generation. A method of generating energy in a power plant comprising a gas turbine includes a compressor section having two or more stages including a low pressure compressor and a high pressure compressor, a combustion section in fluid communication with the compressor section, and a combustion section in fluid communication. Generating a flue gas from a gas turbine comprising an expanded section, recirculating the flue gas to a low pressure compressor, and a carbon dioxide (CO ₂ ) separator for a portion of the compressed recirculated flue gas flushed binary, the method comprising diverting the remainder of the high pressure compressor, and generating a CO ₂ lean gas to separate CO ₂ from the diverted portion in a CO ₂ separator, the remainder of the recirculated flue gas Supplying to the high pressure compressor.

Configured power plant as CO ₂ emissions are reduced, and the compressor section having two or more compression stages comprising (a) (i) high pressure compressor in fluid communication with the low pressure compressor, (ii) compression A combustor having a first inlet for introducing gas, a second inlet for introducing fuel, and an outlet for discharging hot flue gas; and (iii) for introducing hot flue gas a gas turbine and a main expander section having an inlet and an outlet in fluid communication with the low pressure compressor, (b) CO ₂ separator in fluid communication with the low pressure compressor for receiving a portion of the flue gas from the low pressure compressor A CO ₂ separator for supplying CO ₂ lean gas to an additional expander, the remaining part of the flue gas being passed to the high pressure compressor via a low pressure compressor in fluid communication with the high pressure compressor Supplied directly It is.

In another embodiment, configured power plant as CO ₂ emissions are reduced, the compressor section having two or more compression stages comprising (a) (i) high pressure compressor in fluid communication with the low pressure compressor (Ii) a combustor having a first inlet for introducing compressed gas from a high pressure compressor, a second inlet for introducing fuel, and an outlet for discharging hot flue gas; iii) a gas turbine comprising an inlet for introducing discharged hot flue gas and a main expander section having an outlet in fluid communication with the low pressure compressor; and (b) low pressure compression to treat a portion of the flue gas. A CO ₂ separator in fluid communication with a humidifier flue gas comprising a CO ₂ separator for supplying humidified and regenerated flue gas by supplying CO ₂ lean gas to a humidifier downstream of the CO ₂ separator And fluid communication with the high-pressure compressor A second expander / compressor unit having a closed outlet is driven, and the remainder of the flue gas is fed directly to the high pressure compressor via a low pressure compressor in fluid communication with the high pressure compressor.

In another embodiment, a method for generating energy at a power plant includes generating flue gas in a gas turbine comprising a combustion section in fluid communication with a compressor section and an expander in fluid communication with the combustion section; A portion of the recirculated flue gas to a carbon dioxide (CO ₂ ) separator downstream of the compressor and a remaining portion to the combustor; ₂ comprising the steps of a shunt flue gases part separator to separate CO ₂ to produce a CO ₂ lean gas, and supplying the remainder of the recirculated flue gas to the combustor. This system can be used in gas turbines with two or more compression stages, and this embodiment can also be applied to gas turbines with single stage compressor units, fluid extraction downstream of the compressor. And reinjection.

  A better understanding of the present invention can be obtained by reference to the following detailed description and examples of the various features of the present invention. In the accompanying drawings, like parts are designated by like numerals throughout the drawings.

The present invention provides a method for reducing CO ₂ emissions by separating high pressure, high concentration CO ₂ at power plants that utilize gas turbines for power generation. As described in more detail below, a high gas pressure is achieved by extracting the recirculated CO ₂ rich flue gas in the middle of the compression path of the gas turbine. As a result, the CO ₂ concentration in the working fluid is increased by the recirculation of the flue gas, and the CO ₂ partial pressure is further increased. When the concentration and the partial pressure of CO ₂ is increased, the energy penalty for removing CO ₂ is that to reduce the observed. Furthermore, since CO ₂ is separated under pressure, the volume flow to be treated is significantly reduced compared to the atmospheric pressure process. Therefore, not only can the separation apparatus be miniaturized, but also the energy required for separation can be reduced. Further, as described below, by a significant increase in CO ₂ partial pressure, for example, selective adsorption and membrane separation other CO ₂ recovery method, such as it is possible.

In this process, part of the fluid extracted from the gas turbine only (e.g. 10% to 70%) to flow to the intermediate cooling CO ₂ separator, the remaining portion is returned to the high pressure compressor and the combustor. This not only increases the partial pressure of CO ₂ in the gas turbine working fluid, but also reduces the volume of gas to be processed in the CO ₂ separator. The cycle configuration is that all cycle flue gas is exhausted from the system via a CO ₂ separator, resulting in maximum CO ₂ capture (preferably greater than 80%). Fresh air for combustion is compressed in a separate compressor unit and enters the gas turbine cycle from the compressor inlet. In this way, dilution of the recirculated CO ₂ rich flue gas before it is introduced into the separator is avoided. In order to minimize the work required for the compression of fresh air, compressed CO ₂ lean gas from the CO ₂ separator may be fed to a separate expander, which is not essential, but preferably air compression. Mechanically connected to the machine. Preferably, various heat recovery methods can be used to maximize the amount of work generated by the expander. For example, a heat exchanger may be used between a fresh air stream exiting the compressor and a clean flue gas stream entering the expander. In another preferred configuration, heat exchange for heat recovery may occur between the CO ₂ rich flue gas supplied to the separator and the CO ₂ lean flue gas exiting the separator.

In a variation of this method, a high gas pressure is achieved by extracting the recirculated CO ₂ rich flue gas downstream of the compressor unit. As a result, the CO ₂ concentration in the working fluid is increased by the recirculation of the flue gas, and the CO ₂ partial pressure is further increased. When the concentration and the partial pressure of CO ₂ is increased, the energy penalty for removing CO ₂ is that to reduce the observed. Furthermore, since CO ₂ is separated under pressure, the volume flow to be treated is significantly reduced compared to the atmospheric pressure process. Therefore, not only can the separation apparatus be miniaturized, but also the energy required for separation can be reduced.

Referring now to FIG. 1, an exemplary power plant 10 with a gas turbine 12 is shown. The gas turbine 12 generally includes a compressor section 13 that includes two or more compression stages as appropriate (eg, a low pressure compressor 14 in fluid communication with the high pressure compressor 16), a combustion chamber 18, compressors 14, 16 and power generation. One or more expander sections 21 (for example, a high-pressure expander 22 to which combustion gas is sent and a low-pressure expander 24 downstream thereof) are provided for supplying energy necessary to drive the generator 26. At start-up, the compressor section 13 supplies a compressed fluid (eg, air or oxygen enriched air) to the combustor 18 where it is mixed with the fuel 20 and combusted to produce gas, particularly including water and CO _2. To do. If the energy of the expander exhaust gas is used in a heat recovery bottoming cycle (for example, a steam Rankine cycle), the efficiency can be increased by, for example, heat recovery and the steam generator 28, and heat is recovered in the form of steam. The gas turbine outlet stream can be fully or partially recirculated. Partial recirculation can be used for transient operation (start, load change, stop). In this case, part or all of the gas exiting the gas turbine flue gas is extracted and used for the desired transient operation. The flue gas (indicated by reference numeral 32) is first cooled by the condenser 30 to remove the generated liquid water, and then recycled to the low-pressure compressor 14. The device may preferably be configured to capture particulates and gas contaminants. As will be described in detail below, a portion 34 of the flue gas recirculation 32 is compressed and sent to the separator 36 (eg, 10-70%), while the remaining portion 38 further includes the high pressure compressor 16 and combustion. recycled to vessel 18 further increases the CO ₂ concentration in the working fluid.

During operation, the recirculated flue gas 32 is compressed by the first compressor 14 to about 2-20 bar. The portion of the compressed gas sent to the CO ₂ separator 36 may be appropriately cooled with an additional heat exchanger or trim cooler 42. The remaining recirculated portion (steam 38) is mixed with fresh air introduced into the cycle through an additional compressor 48. The air-fuel mixture may be appropriately cooled by the intercooler 51. In the basic principle of intercooling, the gas is partially compressed and then cooled before it is finally compressed to the desired pressure (ie with the compressor 16). Thus, the compression work is reduced by the intercooler 51, and the output of the circulation process is increased. The CO ₂ separation takes place before final compression. Optionally, the trim cooler 42 cools the gas to the desired temperature range for CO ₂ separation. Advantageously, current intercooled aircraft diversion scrolls can be utilized to mitigate the gas turbine modifications required to perform the process.

The clean gas 44 exiting the CO ₂ separator 36 is expanded by an expander 46. Fresh air is supplied by an additional compressor 48 and mixed with the recirculating low pressure flue gas portion 38. The mixed gas is intermediate-cooled 51 and supplied to the high-pressure compressor 16. The expander and air compressor may be connected to an additional motor (M) in the compressor-expander unit. In order to recover waste heat and reduce the power to drive the compressor 16, heat exchange in the heat exchanger 50 may be performed between the air flow and the clean gas flow entering the expander 46. In another configuration, heat exchange for the heat recovery 50 may occur between the CO ₂ rich flue gas exiting the low pressure compressor 14 and the CO ₂ lean flue gas 44 exiting the separator.

As described above, the flue gas recirculation portion 34 can be used to affect the overall CO ₂ separation rate. For the same reason, the flow rate of fresh air to the low-pressure compressor 14 can be adjusted. If the ignition upstream of the expander unit 46 is used, the motor for driving the compressor 48 can be eliminated. A common shaft with the steam turbine or gas turbine 12 can also be used to drive the unit. Intermediate cooling air compressors can also be used because they save compression work. Gas humidification (eg, by steam or water injection or non-adiabatic saturator) on one side of the compressor, upstream of the entire combustor, expander or downstream of the CO ₂ separation unit 36 eliminates the need for additional motors. Not only can it be possible, but also output and cycle efficiency can be increased.

In this method, the CO ₂ concentration of the flue gas is increased in the separator as compared to the traditional post-combustion CO ₂ capture method. Similarly, only a portion of the recirculated flue gas flows through the separator 36 and, more importantly, because the flue gas is pressurized, the volumetric flow to the separator 36 is at atmospheric CO ₂ recovery. Compared with, it is greatly reduced. For example, 50% recirculation of flue gas doubles the CO ₂ concentration and compression increases the CO ₂ partial pressure by 2 to 20 times. As a result, the required dimensions and energy requirements of the CO ₂ separator are reduced. Furthermore, the mass flow rate can be increased by reducing the inlet temperature of the high-pressure compressor 16, and the specific output is increased. In general, a significant increase in the CO ₂ partial pressure also allows for the selection of other CO ₂ recovery methods such as adsorption and membrane separation, as described below.

FIG. 2 shows another embodiment of the power plant 100. In this embodiment, CO ₂ lean gas is used for the internal heat recovery cycle. The CO ₂ lean gas is regenerated (recovered) in the main gas turbine outlet stream. Prior to that, the CO ₂ lean gas may be humidified using low temperature heat from the cycle as appropriate to saturate the gas. This creates an additional internal heat sink in the cycle. A possible effect when using internal heat recovery and / or humidification is a power independent air compressor and increased power. As appropriate, the steam bottoming cycle may be reduced in size or removed from the plant. The invention disclosed herein also includes a configuration comprising two or more gas turbines coupled by gas extraction over compression. In CO ₂ separation by the membrane separation method, the driving force can be increased by using a vacuum pump or the like on the membrane permeation side.

The power plant 100 includes a gas turbine 112 having a compressor section 113 that includes two or more compression stages (eg, a low pressure compressor 114 in fluid communication with a high pressure compressor 116), a combustion chamber 118, One or more expander sections 121 (e.g., a high pressure expander 122 to which combustion gases are sent and a low pressure expander 124 downstream thereof) to supply the energy required to drive the compressors 114, 116 and generator 126 as desired. Is provided. At startup, the compressor section 113 supplies a compressed fluid (eg, air or oxygen enriched air) to the combustor 118, where the combustor 118 mixes with the fuel 120 and combusts, particularly flue gas containing water and CO _2. Is generated. Flue gas is supplied to regenerator 150 and economizer 152 where heat is recovered. Regenerator 150, the waste heat of the turbine exhaust gas stream is recovered, to preheat the CO ₂ lean exhaust gas prior to entering the expander 148, the economizer humidification of optional CO ₂ lean gas were recovered low-grade heat Promote. As above, the flue gas from the expander section 121 can be fully or partially recycled. In the case of partial recirculation, a part of the flue gas emitted from the gas turbine flue gas is extracted, first cooled by the condenser 130 to remove the generated liquid water, and then transient operation (starting, load change, Used for stop). The device may preferably be configured to capture particulates and gas contaminants. The flue gas thus treated (shown at 132) is then recycled to the low pressure compressor 114. As described in detail below, a portion 134 of the flue gas recirculation is sent to the CO ₂ separator 136 at a high CO ₂ partial pressure (eg, 10-70%), while the remaining portion 138 is further pressurized. Recirculated to machine 116 and combustor 118.

During operation, the recirculated flue gas 132 is compressed by the first compressor 114 to about 2-20 bar. The portion of the compressed gas sent to the CO ₂ separator 136 may be appropriately cooled with an additional heat exchanger or trim cooler 142. The remaining recirculated portion (steam 138) may be an additional compressor section 157 (optionally an intercooled additional compressor unit consisting of two or more compressors 158 and 156 and an intercooler 162). ) Mixed with fresh air introduced into the cycle through. The mixture of the recirculated flue gas and fresh air is appropriately cooled by the intercooler 164 and recirculated to the high-pressure compressor 116 and the combustor 118. The clean CO ₂ lean gas 144 flowing out from the separator 136 is appropriately humidified by the humidifying tower 154 to generate a humidified gas 155 and is expanded by the expander 148. By introducing the humidified CO ₂ lean gas 155 directly into the expander 148, the motor for operation of the compressor section 157 coupled to the expander 148 can be eliminated or minimized. Furthermore, the expander 148 can also be used to drive the generator 160 as needed. For example, it will be apparent that the use of low temperature waste heat from 164, 152, 162 can promote humidification of the CO ₂ lean gas. This lower energy is supplied to the humidification tower in the form of high-temperature pressurized water, humidifies the CO ₂ lean gas in a countercurrent manner, and the water itself is cooled. Using this low energy in this way increases the efficiency of the power plant 100 by generating an internal heat sink (ie, cold water flowing out of the tower).

The compressor section optionally includes a low pressure compressor 158 coupled with a high pressure compressor 156. Fresh air (or oxygen enriched air) is supplied to the low pressure compressor 158 and further compressed by the high pressure compressor 156. If appropriate, the gas may be cooled by an intercooler disposed between these compressors. The gas is then mixed with the recirculated low pressure flue gas portion 138 and fed to the intercooler 151 before being introduced into the high pressure compressor 116. The enthalpy of the hot water generated by the optional intercooler can be used to saturate the gas passing through it or the CO ₂ lean gas before being sent to the expanders 48,148.

As explained in the above internal heat recovery method, the use of CO ₂ lean gas has the advantage that the output increases and the compressor becomes a power independent type. Where appropriate, the use of a pair of units 157, 148 that hit the net output can eliminate or reduce the size of conventional steam bottoming cycles.

The method disclosed above was modeled as a gate cycle. Simulation confirms the main effect of recirculating flue gas to the combustor. When recycling 50% of the flue gases to the high pressure compressor 116, the driving force for CO ₂ separation in CO ₂ separator 136 is doubled, investment and energy demand associated the volume flow rate is halved Reduce. The one-step reduction in volumetric flow rate and the increase in CO ₂ partial pressure in the CO ₂ separation unit, and hence the reduction in cost and energy demand, is due to the CO ₂ separation unit operating under pressure. Furthermore, cycle configuration is that discharged from the system normal every cycle flue gases during operation via the CO ₂ separator. This ensures maximum CO ₂ recovery (preferably over 80%). Further, the fresh air for combustion is separately compressed and introduced into the main gas turbine unit, and enters the gas turbine cycle from the high-pressure compressor inlet. This avoids dilution of the recirculated CO ₂ rich exhaust gas before introduction into the separator. In order to minimize the work required for the compression of fresh air, the compressed CO ₂ lean gas from the removal unit is sent through a separate expander mechanically coupled to the air compressor. Preferably, various heat recovery methods can be used to maximize the amount of work generated by the expander. For example, there is heat exchange between a fresh air stream exiting the compressor and a clean flue gas stream entering the expander.

In all of the above technical ideas, the CO ₂ separation method includes, for example, a chemical absorption method using an amine solvent. In the conventional method, the working medium is brought into contact with a solvent in an absorption tower to convert CO ₂ from a gas phase to a liquid phase, and CO ₂ lean gas is discharged. Alternatively, a membrane can be used as a contact element. This has the advantage that the two streams are kept separated, the movement of the solvent into the gas stream is prevented and the turbomachine is protected. In addition, overall dimensions, weight and cost can be reduced. The CO ₂ concentrated solvent exiting the absorption tower or diaphragm unit is regenerated in the separation tower and recycled for reuse. Specific examples of other CO ₂ separation methods include a physical absorption method, a combination of a chemical absorption method and a physical absorption method, adsorption on a solid, and a combination thereof.

It should be noted that when the air (40, 140 or that introduced into the units 48, 158) is oxygen enriched, the volume of air introduced into the combustion process is reduced and the formation of CO ₂ is improved. Therefore, the gas flow rate flowing through the separator is further reduced.

  A significant advantage that the high-pressure separation method described herein has over, for example, an oxy-combustion method is that it can be used with minor modifications to existing turbomachines. This is possible because the characteristics of the working medium are very similar to those in existing gas turbines.

Humidification prior to 16/116 or 48/148 can be achieved by either water injection or steam injection or the use of a humidification tower. All three of these methods make up for the loss of CO ₂ from the working medium by the addition of water vapor. Thus, the volume flow through each expander increases and the output increases. Further, when an existing turbomachine is used, the process performance can be improved by resetting the predetermined design conditions at the expander inlet in this manner.

FIG. 3 illustrates another embodiment of a power plant 200 that includes a gas turbine 202. The gas turbine 202 generally includes a compressor 204, a combustion chamber 206, and one or more expander sections 208 that provide the energy necessary to drive the compressor 204 and the generator 210 for power generation. In one embodiment, the compressed stream 212 from the compressor 204 is split into two parts: a first part 214 that is directed to the combustion chamber 206 and a second part 216 that is directed to the secondary combustor 218. Is done. In the secondary combustor 218, the second portion 216 of the compressed stream 212 is combusted with additional fuel 220 (eg, natural gas). This is done to reduce the oxygen content of the second portion 216 and maximize the CO ₂ concentration.

CO ₂ rich stream 222 is generated by the secondary combustor 218 is led to the CO ₂ recovery system 224, where _CO 2 226 from the CO ₂ rich stream 222 is separated, the CO ₂ lean stream 228 to the secondary turbine system 230 To produce additional output. Optionally, the system may include a plurality of heat exchange contact surfaces, for example, CO ₂ rich stream 222 and CO ₂ lean stream 228 may be directed to heat exchanger 232 for heat exchange therebetween. Further, the heat exchanger 232 can be incorporated directly into the secondary combustor 218 to provide additional heat exchange between the combustion gases and the CO ₂ lean stream 228 and to cool the secondary combustor material.

The secondary turbine system 230 includes a secondary turbine 234 and a secondary compressor 236. The CO ₂ lean stream 228 is sent to the secondary turbine 234 to expand and generate additional power at the motor generator 238. Exhaust gas 240 is generated after being expanded through secondary turbine 234 and can flow to the ambient environment, typically through heat recovery unit 242 to recover the residual heat and release it. Since most of the CO ₂ is removed from the exhaust gas 240 by the CO ₂ recovery system 224, the exhaust gas 240 is substantially free of CO ₂ and can be released to the atmosphere without harming the environment.

  Air 244 is routed through secondary compressor 236, which is typically driven by turbine 234 to produce a compressed air stream 246. The compressed air stream 246 is sent to the combustion chamber 206 and combusted with the primary fuel 248 and the first portion 214 of the compressed stream 212 to produce hot flue gas 250. Hot flue gas 250 expands in expander section 208 and generates power in generator 210 to produce expanded exhaust gas 252. The expanded exhaust gas 252 is sent to the heat recovery steam generator 254 to produce steam 256 and cooled expanded exhaust gas 258. The steam 256 is sent to the steam turbine 260 to expand and further generate electric power. The cooled expanded exhaust gas 258 is sent to the compressor 204. The expanded exhaust gas 258 is typically cooled to a suitable temperature from which water can be removed and sent to the compressor 204 where the exhaust gas is compressed.

  In one embodiment of the invention, the combustion chamber 206 includes a primary combustion zone 262 and a secondary combustion zone 264. In one embodiment, compressed air 246 and primary fuel 248 are sent to primary combustion zone 262 for combustion, and first portion 214 of compressed stream 212 is sent to secondary combustion zone 264.

In one embodiment, a catalytic combustion device (not shown) may be used to remove oxygen from the CO ₂ rich stream 222 for introduction into the CO ₂ capture system 224. Depending separation method while others benefit from a decrease in oxygen partial pressure, for example, decompose at a rate substantially proportional to the oxygen partial pressure many many solvents used in the CO ₂ recovery. Thus, oxygen removal has a beneficial effect on the overall system effectiveness. Although the advantages of this configuration have been described in this embodiment, this configuration is equally applicable to all embodiments of the present invention.

  In the present specification, the present invention has been described using specific examples including the best mode for carrying out the present invention by those skilled in the art. The technical scope of the present invention is defined by the claims, and includes other embodiments that will be apparent to those skilled in the art. Such other embodiments are encompassed by the claims if they have components that do not differ from the claim language or equivalent components that do not differ substantially from the claim language. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified diagram of a power plant according to an embodiment that performs two-stage compression, CO ₂ separation from a partial flow of extracted compressed gas during compression, and reintroduction of compressed gas comprising air and recirculated flue gas. FIG. 6 is a simplified diagram of a power plant according to another embodiment that performs two-stage compression and CO ₂ separation with internal heat recovery using a CO ₂ lean gas recycle product. FIG. 6 is a simplified diagram of a power plant according to another embodiment that performs CO ₂ separation from a partial stream of recirculated exhaust gas extracted downstream of a compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power plant 12 Gas turbine 13 Compressor section 14 Low pressure compressor 16 High pressure compressor 18 Combustion chamber 21 Expander section 22 High pressure expander 24 Low pressure expander 26 Generator 28 Heat recovery and steam generator 30 Condenser 32 Flue gas 34 part ( Flue gas)
36 Separator 38 The rest (flue gas)
42 Trim cooler 44 Clean gas 48 Additional compressor / expander 50 Heat exchanger 51 Intermediate cooler 100 Power plant 112 Gas turbine 113 Compressor section 114 Low pressure compressor 116 High pressure compressor 118 Combustion chamber 120 Fuel 121 Expander section 122 High pressure Expander 124 Low pressure expander 126 Generator 132 Flue gas 134 Part (flue gas)
136 Separator 138 Remaining part (flue gas)
142 trim cooler 144 clean CO ₂ lean gas 148 expander 150 regenerator 152 economizer 154 humidification tower 155 humidification gas 156 compressor 157 additional compressor section 158 compressor 162 intermediate cooler 164 intermediate cooler

Claims (10)

A method for generating energy in a power plant (10, 100) comprising a gas turbine (12, 112), comprising:
A compressor section (13, 113) having two or more stages including a low pressure compressor (14, 114) and a high pressure compressor (16, 116), and a combustion section (in fluid communication with the compressor section (13, 113)) Generating gas from a gas turbine (12, 112) comprising an expander section (21, 121) in fluid communication with the combustion section (18, 118);
Recirculating the flue gas to the low pressure compressor (14, 114);
Diverting a portion of the compressed recycle flue gas to a carbon dioxide (CO ₂ ) separator (36, 136) and diverting the remaining portion to a high pressure compressor (16, 116);
Generating a CO ₂ lean gas to separate CO ₂ from the diverted portion in a CO ₂ separator (36, 136),
Feeding the remainder of the recirculated flue gas to the high pressure compressor (16, 116). The method of any preceding claim, further comprising mixing fresh air with the remainder of the recirculated flue gas prior to diversion to the high pressure compressor (16, 116). The method according to claim 1 or 2, wherein the remaining part of the recirculated flue gas passes through the intercooler (51,164) before entering the high-pressure compressor (16,116). Some of the flue gas CO ₂ separator into (36, 136) is from about 10 to about 70% of the recycle flue gas, any one method according to claims 1 to 3. The method according to any one of claims 1 to 4, wherein more than 50% of the CO ₂ is removed in the step of separating the CO ₂ from the diverted portion with a CO ₂ separator (36, 136). 6. Any one of claims 1 to 5, wherein all flue gas from the gas turbine (12, 112) is discharged from the power plant (10, 100) via a CO ₂ separator (36, 136). The method described in the paragraph. A power plant (10, 100) configured to reduce CO ₂ emissions, wherein the power plant (10, 100)
A compressor section (13, 113) having two or more compression stages including a low pressure compressor (14, 114) in fluid communication with the high pressure compressor (16, 116), and a first inlet for introducing compressed gas A combustor (18, 118) having a second inlet for introducing fuel (20, 120) and an outlet for discharging hot flue gas; and an inlet and low pressure for introducing hot flue gas A gas turbine (12, 112) comprising a main expander section (21, 121) having an outlet in fluid communication with the compressor (14, 114);
A CO ₂ separator (36, 136) in fluid communication with the low pressure compressor (14, 114) to receive a portion of the flue gas from the low pressure compressor (14, 114), with additional CO ₂ lean gas A low pressure compressor (14) having a CO ₂ separator (36, 136) for feeding to the expander (48, 157), wherein the remaining part of the flue gas is in fluid communication with the high pressure compressor (16, 116). , 114), which is supplied directly to the high-pressure compressor (16, 116). A heat exchanger (disposed between the CO ₂ separator (36, 136) and the low pressure compressor (14, 114) for treating a portion of the flue gas from the low pressure compressor (14, 114). 42, 142). The power plant of claim 7, further comprising: The intercooler (51,164) for receiving and cooling the recirculated flue gas (32,132) before being introduced into the high pressure compressor (16,116). The listed power plant. The power plant according to any one of claims 7 to 9, wherein the gas turbine (12, 112) is connected to one or more additional gas turbines.

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